Antimonide high-power semiconductor laser diodes emitting at 2μm have broad prospects in many fields, such as tunable diode laser absorption spectroscopy. However, power is an important indicator for the application of antimonide semiconductor laser diodes. In this paper, we reported the high-power antimony laser diodes emitting around 2μm achieved in our group. The maximum optical power is 1.001W with injected current 3.04A at working temperature 20℃.
As one of the primary products in the field of semiconductor lasers, GaAs-based semiconductor laser devices with an 808nm wavelength are widely applied in various industries such as industrial, medical, and scientific research. These devices possess substantial market potential. This paper reports on the development of a high-power array semiconductor laser device emitting at 808nm wavelength, achieved by our research team. At a temperature of 25°C, with a filling factor of 30% and an injection current of 50A, the maximum output power reaches 55.31W, and the photoelectric conversion efficiency is 58.74%. This device demonstrates exceptional emission performance.
KEYWORDS: Semiconductor lasers, Antimony, High power lasers, Semiconducting wafers, Epitaxy, Scanning electron microscopy, Quantum technologies, Quantum numbers, Fabrication, Windows
Antimony laser diodes emitting at 2 μm have shown great potential due to the extraordinary performance in gas detecting and other promising fields. However, it is difficult to increase the power of antimony laser diodes, the applications of which would be restricted greatly. In this paper, we report the watt-level antimony laser diodes emitting at 2 μm developed by our group, and the maximum output power can achieve about 1.082W at 20℃ with the injection current set as 5A, showing excellent performance.
High output power GaSb-based diode lasers are critical component for 2μm laser systems. We compare four structures with different layer thickness combinations to optimize lower cladding layer thickness. Four structures have similar optical confinement factor of active region. As the lower cladding layer thins, the threshold current increases and the series resistance slightly reduces. Among the four structures, laser with 370nm waveguide layer and 1200nm n-type cladding layer functions the best. An output power of 1.21W at 3A is obtained, the threshold current is 0.11A, the series resistance is 0.25Ωthe slope efficiency is 0.42W/A.
GaSb-based narrow Ridge Waveguide (RW) laser diodes providing high optical power with low lateral beam divergence single-transverse-mode operation are fabricated and characterized. The typical Separate-Confinement-Heterostructure (SCH) Multi-Quantum-Well (MQW) structure is grown by the solid-state Molecular Beam Epitaxy (MBE). The 1 mm long uncoated RW lasers yield single-transverse-mode output power exceeding 170 mW in the 1950 nm wavelength range under continuous-wave (cw) operation at an injection current of 800 mA and room temperature of 20 ℃. The shallow-etched 7 μm width RW design produces a lateral beam divergence angle as narrow as 9° Full Width at Half Maximum (FWHM) with an excellent beam quality of M2 factor < 2 at the maximum output power, enabling it for simple and inexpensive bulk coupling into the typical SM1950 or PM1950 fiber which has a core diameter of 7 μm and numerical aperture (NA) of 0.2. The RW lasers with high output power, good beam quality, and low divergence are promising candidates for a wide range of demanding and advanced applications including pumping fiber amplifiers and solid-state lasers, seeding external cavity lasers, and frequency conversion.
High power mid-infrared GaSb-based lasers are desired for many applications, however, the self-heating in the active region is still one of the main influence factors for practical application. In this paper, we report on fabrication and characterization of high-power GaSb-based lasers. The temperature dependence of output performance of the device was investigated. Due to the high quality of epitaxy and wide waveguide design, the lasers exhibited a high-power capability from 288 K to 318 K. Devices with a cavity length of 1.5 mm and an aperture of 100 μm delivered a power of 1.46 W at a current of 7 A at 288 K and remains 1.10 W at 318 K under CW operation limited by thermal rollover. The characteristic temperature T0 is 151 K and 68 K below and above 298 K, respectively.
GaSb-based InGaSb/AlGaAsSb double quantum well separate confinement heterostructure laser diodes had been grown by molecular-beam-epitaxy. 1000×100 μm2 stripe-type waveguide LDs with facets coated were fabricated and characterized. The high output power of 1.107 W and peak wavelength of 2.09 μm had got with injected current 5 A at working temperature 20℃. The maximum wall plug efficiency was 28.8% with injection current 0.55 A.
We have fabricated and characterized a narrow ridge waveguide InGaSb/AlGaAsSb type-I separate-confinementheterostructure (SCH) multi-quantum-well (MQW) laser diode emitting near 2.0μm. The broadened vertical waveguide laser structure is grown by the solid-state molecular beam epitaxy. The 4.5μm lateral ridge waveguide results in a single transverse mode operation of the laser with an injunction current below 200mA at a heat sink temperature of 293K. This laser diode provides a room temperature continuous-wave output power of 40mW at a driving current of 200mA with a 1mm cavity length and 97/5% high-reflection/anti-reflection coatings, mounted epi-side down. The far-field beam intensity distribution on the fast and slow axis of the laser diode demonstrates a TE00 fundamental transverse mode laser beam with the fast and slow axis beam divergence of 58°*23° full width at half maximum (FWHM). The diode lasers operating on fundamental spatial mode are efficiently coupling into optical fibers or collimating for free-space applications. The midinfrared region single transverse mode GaSb-based laser is hence an ideal light source for spectroscopic sensing and diodepumping pumping fiber amplifiers and solid-state lasers systems.
The resistivity of each layer constituting a 2μm GaSb-based laser is measured with Van der Pauw method. The operation temperature of GaTe doping source is optimized for lower resistivity. The series resistance contribution of each layer is calculated. A new laser structure is designed, 65% of the optical field distributes in quantum wells and waveguide layers while the series resistance is reduced to 0.28Ω.The laser with new design is fabricated, 0.89W continuous output power at room temperature can be achieved at a current of 3A with voltage of 1.40V. The slope efficiency of the emitter is 0.32W/A, and almost no slope efficiency is observed in the process of increasing current until 2.6A.
An experimental investigation for the polarization analysis of the high power GaSb-based semiconductor laser diodes emitting at 2.1μm in terms of measuring Stokes parameters has been exploited and adopted, which gives further insight into understanding, manipulating and applying the polarization properties of the laser diode. Results of output performance and polarization behavior of the laser are presented in the paper. The average linear polarization of the laser diode reaches 97.72% with output power exceeding 1W at 3.5A under CW operation at 20℃, which demonstrates the dominant position of linear polarization light of the output beam. Highly linear-polarized properties could not only enhance the performance of high power GaSb-based laser diodes in traditional applications in laser processing and beam combing, but also open new application fields such as parametric convention and coherent detection.
Mid-infrared spectral region (2-4 μm) is acquiring significant attention due to the presence of various enabling applications in the field of remote gas detection, environmental pollution detection applications. Tm:YAP is an important crystal materials for diode-pumped laser emission of 2μm wavelength. We report a room-temperature diode pumped Tm:YAP thin disk laser. The maximum output power was 3.5 W at wavelength of 1940 nm.
We report on successful fabrication of GaSb-based type-I quantum well distributed Bragg reflector (DBR) lasers emitting around 2.3μm. Second-order Bragg gratings of chromium were patterned by electron beam lithography. For 1.5-mm-long laser diode, single mode continuous-wave operation with output power of 10mW is obtained. The devices show a stable single mode operation with high side mode suppression ratio.
High-power InGaSb/AlGaAsSb quantum well separate confinement structure lasers are fabricated. Threshold currents of the sample lasers range from 150mA to 270mA, turn-on voltages range from 0.51V to 0.59V. Stable high power and high efficiency operation is achieved, output powers at 3A range from 978mW to 1050mW, the power conversion efficiencies at 3A range from 21.3% to 22.9%, slop efficiencies range from 0.35W/A to 0.38W/A. The capability of fabricating reliable high-power 2μm GaSb-based laser is confirmed. The current of one sample was ramped up to 6A, the emitter exhibits a high performance with peak output power of 1320mW at 5.4A,maximum power conversion efficiency of 27.5% and slop efficiency of 0.34W/A.
The growth conditions and lasing characteristics of the optically barrier-pumped GaSb - based semiconductor disk laser (SDL) emitting near 2 μm in an external cavity configuration are reported. It is made of a GaSb/AlAsSb Bragg reflector, a Ga0.8In0.2Sb/GaSb multi quantum-well active region and an Al0.8Ga0.2As0.03Sb0.97 window layer. Using an intracavity SiC heat spreader, a cw output power in excess of 1.12 W has been achieved at a heat sink temperature of 0 °C.
We report the optimum growth parameters of InAs/AlSb superlattices (SLs) for interband cascade lasers (ICL) grown by the solid-source molecular beam epitaxy(MBE). The InAs/AlSb superlattices samples were grown on GaSb substrate at different temperatures and characterized by high resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and photoluminescence (PL). By changing the group-Ⅴ flux ratio during the SLs growth, the InAs/AlSb superlattices matched to GaSb substrate were obtained. Subsequently, the SLs were grown at different growth temperature. By photoluminescence we found the highest PL intensity was obtained when the SLs samples were grown at 458°C and the PL wavelength is at 1730 nm. From 10 × 10 μm2 AFM image, we found the root mean square (RMS) of the sample grown at 458°C was 1.96 Å which indicates the low surface roughness and god surface morphology.
We report on the fabrication of GaSb-based type-I quantum well distributed Bragg reflector (DBR) lasers operating in the 2-μm region. Second-order metallic gratings of chromium are patterned by electron beam lithography. The fabricated DBR lasers emit a single-mode continuous wave at 2.04 μm. The side mode suppression ratio (SMSR) is as high as 35dB with a narrow line-width of 37MHz. The devices show a stable single mode operation with current tuning rate of 0.006nm/mA.
We demonstrated high power semiconductor diode lasers emitting around 2.1 μm with the micro-stripe broad area (MSBA) structure which was proposed to improve the broad area (BA) lasers’ lateral beam quality. 1.28W output power at 7A at continuous wave (CW) operation was achieved from the uncoated MSBA laser. It is shown that the micro-stripe structure would lead to worse threshold current and slope efficiency of the lasers because of the less-pumped lossy regions. However, the MSBA lasers would have better heat dissipation system with proper micro-stripe structure and gain advantages on power performance at high currents.
We report the wavelength tuning of type-II “W” quantum well of interband cascade laser. By changing the thickness of the InAs electron well, the wavelength of the active region is adjusted. We found that the whole 3-4 μm spectra can be realized and the intensity was basically the same by measuring the photoluminescence (PL) of the active region. It showed that the type-II “W” quantum well of interband cascade laser can achieve 3-4 μm range without attenuation. In addition, we calculated the wavelength of quantum well of different InAs thickness by the 8-band k·p method. And we found that the wavelength of the active region varies with the thickness of the InAs electron well, which is consistent with the theory. In addition, the measured wavelength was different from the theoretical wavelength, which may be due to the As incorporation. The incorporation of As into the InGaSb layer will lead to blue shift in the wavelength.
Here we report the solid source molecular beam epitaxy (MBE) growth of high quality of InGaAs/ GaAs quantum dot (QD) structures. A laser device is fabricated by the semiconductor process, including Lithography, Inductively Coupled Plasma (ICP), Plasma Enhanced Chemical Vapor Deposition (PECVD) and Reactive Ion Etching (RIE). The rigid is 100μm wide and cavity is 2000um long. Room temperature continuous-wave (CW) operation with emission wavelength around 1.31μm is presented. Threshold current (Ith) and threshold current density (Jth) is 0.3A and 150A/cm2 at 15°, and output power at Ith=7A reached as high as 1.079W. We also observe that the spectrum shift from 1315nm to 1333nm when the injection currents increase from 1.5A to 3.5A, and the shift speed is 8.72 nm/A.
The semiconductor epitaxial design and lasing characteristics of an optically barrier-pumped GaSb -based semiconductor disk laser (SDL) emitting at 2.0 μm optimized for resonant optical barrier pumping around 1470 nm are presented. Compared to conventional barrier-pumped devices with pump wavelength of 980nm, the novel barrier-pumped device with the smaller quantum deficit reaches a significantly higher power efficiency, and thus a higher output power at a given pump power, due to the lesser internal heat generation. Using an intracavity SiC heat spreader, a cw output power in excess of 300 mW has been achieved at a heat sink temperature of +15 °C, and still more than 500 mW at +10 °C.
High power GaSb based type-I GaInAsSb/AlGaAsSb three quantum wells laser diodes emitting at 2.4 μm were optimized and fabricated. The laser wafer was grown with solid source Molecular Beam Epitaxy System. With optimizations of the epitaxial structure design and the ohmic contact, the operation voltage and the internal loss decreased; the internal quantum efficiency and output power increased. The internal quantum efficiency was determined about 80.1% and the internal loss was 12 cm-1 by measuring laser diodes with different cavity lengths. An uncoated 2-mm-long laser diode with 90-μm-wide aperture exhibited a threshold current density of 222 A/cm2 (74 A/cm2 per quantum well), a continuous wave output power of 232 mW and a quasi-continuous wave (1 kHz, 10 μs) output power of 1 W at room temperature.
2.X μm InGa(As)Sb/AlGaAsSb compressively strained quantum wells laser has been grown and fabricated. Antimonide laser with 1.5mm*90μm without AR/HR emitted 550mW of continuous wave output power at 2μm.And 2.4μm laser without AR/HR output 195mW at room temperature.
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